Simple computer method provides contours for radiological images

Computer is provided with information concerning boundaries in total image. Gradient of each point in digitized image is calculated with aid of threshold technique; then there is invoked set of algorithms designed to reduce number of gradient elements and to retain only major ones for definition of contour

SAR antenna calibration techniques

Calibration of SAR antennas requires a measurement of gain, elevation and azimuth pattern shape, boresight error, cross-polarization levels, and phase vs. angle and frequency. For spaceborne SAR antennas of SEASAT size operating at C-band or higher, some of these measurements can become extremely difficult using conventional far-field antenna test ranges. Near-field scanning techniques offer an alternative approach and for C-band or X-band SARs, give much improved accuracy and precision as compared to that obtainable with a far-field approach

A Wii Bit of Fun: A Novel Platform to Deliver Effective Balance Training to Older Adults

BACKGROUND: Falls and fall-related injuries are symptomatic of an aging population. This study aimed to design, develop, and deliver a novel method of balance training, using an interactive game-based system to promote engagement, with the inclusion of older adults at both high and low risk of experiencing a fall.STUDY DESIGN: Eighty-two older adults (65 years of age and older) were recruited from sheltered accommodation and local activity groups. Forty volunteers were randomly selected and received 5 weeks of balance game training (5 males, 35 females; mean, 77.18 ± 6.59 years), whereas the remaining control participants recorded levels of physical activity (20 males, 22 females; mean, 76.62 ± 7.28 years). The effect of balance game training was measured on levels of functional balance and balance confidence in individuals with and without quantifiable balance impairments.RESULTS: Balance game training had a significant effect on levels of functional balance and balance confidence (P Peer reviewedFinal Published versio

Square Patterns and Quasi-patterns in Weakly Damped Faraday Waves

Pattern formation in parametric surface waves is studied in the limit of weak viscous dissipation. A set of quasi-potential equations (QPEs) is introduced that admits a closed representation in terms of surface variables alone. A multiscale expansion of the QPEs reveals the importance of triad resonant interactions, and the saturating effect of the driving force leading to a gradient amplitude equation. Minimization of the associated Lyapunov function yields standing wave patterns of square symmetry for capillary waves, and hexagonal patterns and a sequence of quasi-patterns for mixed capillary-gravity waves. Numerical integration of the QPEs reveals a quasi-pattern of eight-fold symmetry in the range of parameters predicted by the multiscale expansion.Comment: RevTeX, 11 pages, 8 figure

Systematic derivation of a rotationally covariant extension of the 2-dimensional Newell-Whitehead-Segel equation

An extension of the Newell-Whitehead-Segel amplitude equation covariant under abritrary rotations is derived systematically by the renormalization group method.Comment: 8 pages, to appear in Phys. Rev. Letters, March 18, 199

Navigation for Spin Stabilized Deep Space Planetary Spacecraft

Navigation for planetary missions is well understood as shown by the successful flights to Venus and Mars by the JPL Mariner spacecraft. However, when we consider the farther planets, such as Jupiter and ultimately Pluto, the trip time requirements are so .long (on the order of 2 years to Jupiter and 8 to 1 0 years to Pluto) that spacecraft reliability becomes the paramount consideration. A basic approach to achieving reliability is to simplify the spacecraft system as much as possible within the limits of mission objectives, which usually arise from the scientific payload. System simplicity and reliability can be greatly enhanced if the spacecraft system is spin stabilized, since this reduces control system requirements substantially and in general minimizes onbeard navigation tasks. However, spin stabilization itself imposes a number of problems which must be solved before such a simplifying technique can be adapted. As an illustration, the present Pioneer VI spacecraft is spin stabilized and has no onboard control requirements after the first few days of the mission; hence its lifetime appears to be limited only by the lifetime of the electronic components. Pioneer VI, shown in Figure 1, is injected in a heliocentric orbit while spinning and is then torqued by a nitrogen system to place its spin axis perpendicular to the plane of the ecliptic. A phased array antenna mounted along the spin axis then provides a fan beam pattern lying in the plane of the ecliptic, thus always illuminating the earth and assuring the constant communication with the DSIF for ranges up to 2 AU. All perturbing factors, such as solar pressure, have been accounted for and this spacecraft will apparently retain its attitude indefinitely. (There is a small change in body attitude during the course of 1/2 of the orbit around the sun but this change is cancelled out in the next 1/2 of the orbit)

Unbiased bases (Hadamards) for 6-level systems: Four ways from Fourier

In quantum mechanics some properties are maximally incompatible, such as the position and momentum of a particle or the vertical and horizontal projections of a 2-level spin. Given any definite state of one property the other property is completely random, or unbiased. For N-level systems, the 6-level ones are the smallest for which a tomographically efficient set of N+1 mutually unbiased bases (MUBs) has not been found. To facilitate the search, we numerically extend the classification of unbiased bases, or Hadamards, by incrementally adjusting relative phases in a standard basis. We consider the non-unitarity caused by small adjustments with a second order Taylor expansion, and choose incremental steps within the 4-dimensional nullspace of the curvature. In this way we prescribe a numerical integration of a 4-parameter set of Hadamards of order 6.Comment: 5 pages, 2 figure

An Analysis of Factors Affecting the Oxygen Consumption of the Isopod Ligia oceanica

This is the publisher's version, also available electronically from http://www.jstor.org/stable/info/30155682A multiple-regression equation was derived in which the statistical significance of the effects of six independent variables on metabolic rate could be arranged in the following order: exposure temperature, body weight, starvation period, feeding period, acclimation temperature, and percentage of lipids. Two multiple-regression equations were required to express the metabolism of Ligia oceanica without loss of accuracy when reapplied to the individual experimental data. One equation accounted for 84% of the variation of metabolism in animals acclimated to 5 or 12 C; the second accounted for 85% of the variation of metabolism in animals acclimated to 18 or 26 C. The rate:temperature curve for aerobic metabolism was sigmoid. A region of reduced temperature sensitivity occurred at intermediate exposure temperatures. Thermal acclimation had little effect on the level of metabolism of well-fed Ligia. The maximum metabolic rate shifted from 27.6 C in fed animals acclimated at 5 C to 28.2 C in those acclimated at 12 C, to 33.1 C in those acclimated at 18 C, and to 33.4 C in those acclimated at 26 C. The region of reduced temperature sensitivity shifted from 15-25 C at low acclimation temperatures to 20-35 C at high acclimation temperatures. The effects of starvation on oxygen consumption are controlled by body size, duration of starvation, and acclimation temperature. Metabolism is suppressed in small animals sooner than large ones at each acclimation temperature; high acclimation temperatures enhance the onset and magnitude of such effects. Exposure temperature and the period of starvation influenced the effect of body size on metabolism